1. Field of the Invention
The present invention relates to a Local Area Network (LAN) interfacing apparatus, in particular to a retransmitting control circuit of an internet interfacing apparatus using the LAN.
2. Background of the Related Art
FIG. 1 illustrates a related art LAN system using an Ethernet protocol. As depicted in FIG. 1, a plurality of the LAN interfacing apparatus 120˜123 are connected to the LAN.
The LAN mainly uses the Ethernet protocol known as a CSMA/CD (Carrier Sense Multiple Access/Collision Detect). The LAN interfacing apparatus 120˜123 are connected to the Internet using the LAN. However, since most of the Ethernet protocols use a half duplex method, the Ethernet protocols cannot receive and transmit at the same time. Accordingly, the LAN interfacing apparatus 120–123 detect an access state of the LAN, and transmit data only when the other LAN interfacing apparatus are not accessing the LAN (in an idle state for 9.6 μs). In other words, a given LAN apparatus transmits data only when the other LAN interfacing apparatus are in a non-transmission state.
The LAN interfacing apparatus 120˜123 connected to the LAN are physically placed apart from each other. Accordingly, more than the two LAN interfacing apparatus may try to transmit data at the same time after detecting the non-transmission state of the other LAN interfacing apparatus. At this time, a data collision occurs on the LAN. Collisions can occur frequently when there is heavy traffic on the LAN.
For example, when a data collision occurs, the corresponding LAN interfacing apparatus 120 outputs a jam signal to the other LAN interfacing apparatus 121˜123 to stop the data transmission. Thereafter, the LAN interfacing apparatus 120 waits for a backup time (equal to an integer times 52 μs) defined in the CSMA/CD specification, and retransmits the data.
FIG. 2 is a block diagram illustrating the related art LAN interfacing apparatus 120˜123. As shown in FIG. 2, the LAN interfacing apparatus comprises an Ethernet controller 10, which performs a control operation for the LAN interfacing, a codec 20 which codes and decodes the transmission/reception data, and a transceiver 30, which transmits/receives the data and detects collisions on the LAN.
To perform data transmission, the Ethernet controller 10 outputs a transmission enable signal TENA, a transmission clock signal TCLK, and a transmission data TXD to the codec 20. The codec 20 codes the received transmission data TXD and outputs it to the transceiver 30. The transceiver 30 outputs the coded data to the LAN and thus connects to the internet.
To receive data, the transceiver 30 receives the data from the LAN and outputs it to the codec 20. The codec 20 decodes the received data RXD and outputs it to the Ethernet controller 10, along with a reception enable signal RENA and reception clock signal RCLK.
Meanwhile, the transceiver 30 additionally performs a function of detecting data collisions on the LAN. Thus, if the transmission data TX± and the reception data RX± are detected at the same time, the transceiver 30 outputs a control signal to the codec 20. The codec 20, in turn, outputs a collision signal CLSN informing the Ethernet controller 10 of the data collision.
When the collision signal CLSN is inputted, the Ethernet controller 10 waits for a prescribed time (integer times 52 μs) in accordance with a back-off algorithm, and then retransmits the data. If the data collision occurs repeatedly, the Ethernet controller 10 retransmits the data up to sixteen times. When the data collision occurs on the same frame after the sixteen retransmission attempts, the Ethernet controller 10 judges it as a transmission failure and performs the retransmission again by using software (S/W).
As described above, the related art LAN interfacing apparatus has several problems. For example, it uses the Ethernet as a LAN protocol. However, when the Ethernet protocol is used, data collisions can occur frequently during periods of heavy traffic on the LAN. Accordingly, data collisions can easily exceed the sixteen retransmission limit, resulting in frequent transmission failures on the background LAN interfacing apparatus using the Ethernet.
Moreover, when the number of data collisions on the LAN exceeds sixteen, the conventional LAN interfacing apparatus performs the retransmission by the S/W. However, this requires additional time (about 10 ms) on an Operating System (OS) to be spent due to the S/W-like task. Accordingly the retransmission speed of the system is lowered.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.